Learn how making certain lifestyle changes can help combat forgetfulness

As we get older, "the brain doesn't literally run out of space, but it becomes less efficient and less able to hold on to as much information," says David Wolk, MD, assistant professor of neurology at the University of Pennsylvania's Penn Memory Center. Beginning in your 30s, two areas of the brain that handle most of your memory processing (the frontal lobes and the hippocampus) gradually begin to shrink. The pathways between nerve cells also start to fray and wither, and messenger chemicals (such as dopamine) that help you encode and retrieve memories start to decline.

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To some extent these changes are unavoidable, but you may be able to slow them down—or at least compensate for them—by making certain lifestyle changes. The key ones to focus on:

Stress Less
You get nervous, you get tongue-tied. Even momentary stress can cause you to lose your train of thought. The reason: Stress hormones such as cortisol interfere with chemicals that brain cells use to communicate, diverting energy from the brain to your muscles. That also makes it more difficult to form new memories, so if you meet someone at a stressful time, you're less likely to remember her name later.

If you're chronically stressed (you often feel overwhelmed and may experience anxiety symptoms like a racing heart and difficulty focusing), that may also predispose you to more serious memory trouble. Women who reported high levels of stress in their 40s and 50s were more likely to suffer from dementia when they got older, according to a 2010 Swedish study. You can help get stress in check by making lists to organize yourself, delegating tasks to others to lighten your load, and taking a few minutes each day to do some deep breathing (research shows it reduces levels of stress hormones) or pursue a hobby you enjoy.

Move More
Moderate exercise such as walking 40 minutes a day three times a week increases the size of the hippocampus in the brain and boosts your body's production of a molecule involved in learning and memory, according to new research at the University of Pittsburgh. If that sounds like a lot of time, don't worry. One study found that middle-aged women who got moderate activity for just 20 minutes twice a week had a 52 percent lower risk of developing dementia later in life. And you can rack up activity throughout the day (walk to do your errands instead of driving, take the stairs instead of the elevator, and so on).

Make Sleep a Priority
Not getting enough sleep makes it difficult for your brain to pay attention to new info and remember it, according to research on people whose shuteye is disrupted by sleep apnea (a condition in which you stop breathing for several seconds at a time during the night). Sleep also appears to play a major role in storing memories. Researchers think that deep, dreaming-stage sleep is especially helpful for locking in facts and "procedural" memories, such as how to play the piano or ride a bike.
Most of us need at least seven hours of sleep per night. If you haven't been getting enough, try turning in 10 minutes earlier each night until you reach your goal. And if you frequently toss and turn—or are waking up in the morning after seven or more hours and still feeling groggy—see your doctor. You may have sleep apnea or another sleep disorder and need treatment.

Eat Your Vitamins
Research has suggested that higher levels of antioxidants in the blood—especially vitamin C, vitamin E and beta-carotene—are associated with better memory performance in older people. Antioxidants may help by reducing cell damage in the brain and improving communication between neurons. Load up on them by eating lots of colorful fruits and vegetables such as blueberries, oranges and red bell peppers.

Also consider getting more vitamin B12, which promotes healthy nerve function and can affect memory. "It's not uncommon to lack B12 as you age, starting as young as your 30s," says Charles Bernick, MD, of the Cleveland Clinic's Lou Ruvo Center for Brain Health. A 3-oz serving of sockeye salmon, rainbow trout or sirloin steak meets or exceeds the recommended daily amount. Fortified breakfast cereal, milk, eggs and Swiss cheese also provide significant amounts of B12.

Stay at a Healthy Weight
Obesity has been linked to memory problems, possibly because being overweight probably means you're not eating well or exercising enough, which impacts your memory, says John Gunstad, PhD, associate professor of psychology at Kent State University. One study published in the journal Neurology found that people who were overweight or obese at midlife were 80 percent more likely to develop dementia later on than those with a normal body mass index. "Even being mildly overweight—having a body mass index over 25—can interfere with your ability to learn new information and recall it later," says Dr. Gunstad.

If you're obese (your body mass index is 30 or more), the danger is even greater, most likely because many obese people have weight-related conditions that interfere with blood flow to the brain, such as high blood pressure, diabetes and sleep apnea. The good news is that losing weight helps dramatically: A recent study led by Dr. Gunstad found that people who had weight-loss surgery tended to have improved memory and concentration 12 weeks after their operations.